In order to minimize evaporation losses of liquid in liquid storage tanks, it is known that internal covers of aluminum or steel can be employed. These covers float on the surface of the liquid and have peripheral seals which engages the inner walls of the tanks in which they are disposed.
Such a cover consists of a deck resting upon pontoons which float in the liquid and float support the deck. Adjacent pontoons, horizontally elongated, are disposed end to end along the direction of elongation. Downwardly depending legs disposed between adjacent ends of adjacent pontoons are secured thereto, these legs having the function of supporting the deck and pontoons above the bottom of the tank when the liquid stored therein is removed.
Initially, the legs were welded or otherwise rigidly secured to the pontoons since this arrangement enhanced the strength of the structure. However, it was discovered that, under certain conditions, internal turbulence in the liquid could cause the buildup of stresses which would in turn cause the deck to flex to an extent at which the pontoon ends secured to the legs could break away from the legs and cause the entire structure to fail.
One solution to this problem shown in U.S. Pat. No. 4,244,487 was to allow one end of a first pontoon to remain rigidly secured to a leg while connecting the end of a second pontoon previously secured rigidly to this leg to the leg in such manner that the second pontoon could pivot with respect to the longitudinal axis of the first pontoon when the deck is flexed.
This solution, however, while it does minimize the reaction of the deck, legs and pontoons to internal turbulence, does not fully eliminate the reaction whereby the deck can still deform and break under conditions of extreme turbulence.
The present invention is directed toward a new type of leg-pontoon connection which essentially eliminates the risk that the deck will deform and break subjected to extreme turbulence.